Iowa's 2.1 million acres of forest are critical for soil conservation,
water quality, wildlife habitat, outdoor recreation and aesthetic pleasure. The
forest resource (92%) is largely controlled by private landowners. Iowa's
forests are dominated by oak-hickory and sugar maple-basswood in the uplands
and silver maple-ash-cottonwood in the bottomlands.

Iowa's trees not only increase the quality of life for all residents,
but they also provide the livelihood for many. In 1996, the wood products
industry in Iowa provided 7,000 jobs, with a combined payroll of $142 million.
Private landowners sold $12 million worth of timber; a total of 77.9 million
board feet of timber were harvested in the state, and 300 wood products firms,
including 71 sawmills, processed the timber. Gross sales of wood products
exceeded $850 million.

Special Issues

The Iowa Department of Natural Resources monitors forest and
tree health in order to determine overall forest and tree health conditions,
the status of natural and exotic insect and disease problems, and to provide
up-to date information for private and public land managers. Estimates of
serious forest and tree health problems were determined by aerial surveys of
over 64,500 acres of representative forested areas across the state during
summer of 1996. Visual surveys from DNR Foresters, municipal foresters, and
trained volunteers were also evaluated, as well as results from the Plant
Disease Clinic at Iowa State University, to determine forest and tree health
conditions and distribution. The issues which impact the highest acreage are
shown in the graph.

Oak Wilt continues to be the most serious forest health issue in
Iowa. An estimated 4,167 new acres were affected by oak wilt in 1996. Although
all species of oak are susceptible, tree in the red oak group often die within
weeks of infection. The fungus moves from tree to tree via root grafts, so the
disease often occurs in pockets. New pockets are caused by overland spread of
fungal spores by sap-feeding beetles. To prevent establishment of new infection
centers, avoid pruning or wounding oaks in the spring and early summer (because
the beetles are attracted to the open wounds). Also, spread of established
pockets can be stopped by severing root grafts between diseased and healthy
trees.

Dutch Elm Disease has re-emerged as a serious forest health
concern in Iowa in 1996. Much of the re-emergence of DED is due to weather
conditions over the past few years that have been favorable to the bark beetles
that vector the disease, and due to an increase in the number of 20- 30
year-old American elms that have naturally regenerated in bottomland areas
across the state. Lack of sanitation and removal of infected trees over the
last few years has contributed to the increase by providing breeding sites for
bark beetles, which then carry the fungus to neighboring elms.

Flooding in late June through July in Western Iowa impacted over
1200 acres of riparian forests along the Missouri, Nishnabotna and Soldier
Rivers.

Browsing damage by white-tailed deer continued to cause
extensive damage to forest and Christmas tree plantations and natural
regeneration across the state. In 1996, approximately 800 acres of forest
planting were documented as receiving severe browse damage, and increasing
amounts of damage to horticultural crops are occurring in the urban/rural
interface.

Diplodia Tip Blight, combined with Dothistroma needle
blight, continue to damage non native conifer plantations, windbreaks and
ornamental planting of Austrian pine, red pine, ponderosa pine and Scotch pine.
Sources of the fungus increased due to continued humid conditions in 1995-96,
and is forcing stand conversions from conifer plantations to native hardwoods
on several state forest areas.

Ash
Yellows, a recently discovered disease that causes slow growth and
chronic decline of ash, impacted scattered green and white ash in the Eastern
and Central portions of Iowa. Urban ash trees are also affected and cooperative
studies with ISU and the Forest Service are continuing.

Other Issues

The Iowa DNR continues to work cooperatively with the State
Entomologist of the Iowa Department of Agriculture and Land Stewardship to
detect, monitor, and eradicate spot infestations of gypsy moth. In 1996, 5241
pheromone survey traps were placed and monitored to determine the presence of
gypsy moth. A total of 25 acres in two locations (Independence and
Spirit Lake) were successfully treated with the biological control agent
Bacillus thuringiensis. Another eradication treatment is planned for 1997 in
the city of Dundee, where infested nursery stock was planted a couple of years
ago. Adult male moth trapping across the state yielded 104 moths in 1996, an
increase of over 35% from 1995. Of particular concern is the disturbingly high
number of moths caught over the 11 northeastern counties of the state. In 1997,
trapping will be intensified in this area in order to determine the location
and size of any gypsy moth infestations.

Urban and community tree health
is impacted by many environmental stresses, such as severely compacted soils,
herbicide injury and mower damage. These stresses often allow opportunistic
insects and diseases the chance to become established and cause gradual tree
dieback and mortality. The impact of the floods of 1993 were not only
felt by trees near waterways but also by trees growing in saturated, poorly
drained clay soils. These saturated conditions, combined with secondary
insects and diseases, have caused additional tree losses in 74 Iowa
communities. Over 2500 maturing white oaks were removed in urban settings due
to sudden crown decline and tree mortality. Evidence of 2-lined Chestnut
Borer and Armillaria root disease were common.

Weather
conditions during 1996 were stressful to many tree species. The winter-spring
of 1996 was below normal in temperature and above normal in precipitation.
Extreme low temperatures (below zero) during February, followed by a cool/wet
spring, delayed bud break by an average of 2 to 3 weeks beyond normal
across the state. Severe winterburn impacted conifer windbreak planting
across northern Iowa. Cooler than normal temperatures prevailed throughout the
months of summer and autumn.

For More Information

William Farris, State Forester Division of Foresters and
ForestryDept.
of Natural Resources Wallace State Office Building Des Moines, IA
50319-0034